1. Technical Field
The present invention relates mainly to a liquid ejection apparatus used as an inkjet type recording apparatus that forms dots on a recording medium by ejecting ink droplets from nozzles in accordance with printing data and a method of initial filling of the liquid ejection apparatus.
2. Related Art
As a liquid ejection apparatus that ejects liquid onto a target, an inkjet type recording apparatus that performs printing by ejecting ink onto a recording paper sheet is known. This type of apparatus suppresses noise generated through printing to a relatively low level and is capable of forming small-sized dots at a high density. Therefore, an inkjet type recording apparatus is now frequently used for printing including color printing. Such apparatus includes an inkjet type printing head and a paper feeder mechanism. Ink is supplied from an ink cartridge to the printing head. The paper feeder mechanism transports a recording medium in a direction perpendicular to the scanning direction of the printing head.
The inkjet type recording apparatus performs recording by ejecting ink droplets onto the recording medium through mechanical pressure or thermal energy applied to the printing head while moving the printing head mounted in a carriage along the width of the recording medium (in the main scanning direction). Specifically, a printing head that ejects, for example, black ink and different color inks such as yellow, cyan, and magenta inks is mounted in the carriage of the inkjet type recording apparatus. The recording apparatus performs not only text printing using the black ink but also full-color printing by changing the ejecting proportion of the inks.
Further, to improve the quality of the color printing, a recording apparatus employing ink of a total of six colors, including black, has been developed. The six colors include light cyan, and light magenta as well as the aforementioned colors. Also, there is a demand for an inkjet type recording apparatus capable of performing large-scale printing on large-sized sheets of paper without replacing ink cartridges. In these cases, ink cartridges with increased capacities become necessary for supplying ink to the recording heads. To satisfy the demand, a recording apparatus configured as will be described in the following has been developed. Specifically, for example, ink cartridges are removably mounted not in a carriage but in cartridge holders arranged in securing portions formed at opposite side portions of the body of the apparatus. Ink is supplied from each of the cartridge holders to a printing head through, for example, a flexible tube and an ink supply passage.
This inkjet type recording apparatus can be applied to various types of printing through ejection of ink droplets from nozzle openings of the printing head. The ink cartridges are replaceable in accordance with the purposes for printing. In other words, if printing needs to be carried out with inks of different types than the inks retained in the currently mounted ink cartridges, the ink cartridges are temporarily separated from the apparatus and replaced by ink cartridges retaining desired types of ink. This structure leads to frequent demands for printings of different printing qualities using different types of inks in the same printer.
However, replacement of the ink cartridges is troublesome for the user of the recording apparatus. If an increased number of cartridges needs to be replaced, such troublesome user operation must be repeated a number of times. In a printing apparatus described in JP-A-2003-237100, the types of ink ejected from corresponding nozzle rows can be changed without replacing ink cartridges. Nonetheless, the apparatus does not allow such switching of the ink types in correspondence with the nozzle rows and is not applicable to a case in which the ink types must be switched in correspondence with the nozzle rows.
JP-A-2001-219574 describes a switch structure that allows switching of ink cartridges in correspondence with nozzle rows. However, the switch structure switches the ink cartridges, which are connected to the nozzle rows. Specifically, the number of ink cartridges that are simultaneously connected to each of the nozzle rows is always one. This makes it necessary to perform initial ink filling for each of the ink cartridges before the ink cartridges are initially used, which is disadvantageous. Further, in the recording apparatus having the above-described switch structure, there may be a case in which only one of the cartridges is used. In this case, bubbles may be generated in a corresponding ink passage, leading to a defect in ink ejection.